Clinical characteristics and risk factors of non-mild outcomes in patients with Omicron variant COVID-19 in Shanghai, China

Introduction: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant rapidly appeared in Shanghai, China in early March 2022. Although a few studies have analyzed the risk factors of the severe type, identifying risk factors for non-mild COVID-19 outcomes (general/severe/critical type) which occur with radiographic evidence of pneumonia is lacking.

Methodology: The COVID-19 patients admitted to a district-level designated hospital from April 26 to May 21 were enrolled in this retrospective study. The clinical manifestations and laboratory examinations were analyzed. Logistic regression was employed to evaluate risk factors for non-mild outcomes.

Results: Of the 311 patients, 196 (63.0%) were mild and 115 (37.0%) were non-mild. Among them, 215 cases (69.1%) were unvaccinated. Male, ≥ 60 years age, and chronic kidney disease were risk factors of progressing to non-mild. Patients with more than two comorbidities were more likely to become non-mild, whereas two/booster doses vaccinated patients had a lower risk of developing to non-mild. The median negative conversion days (NCDs) were 12 days. Non-mild, > 2 comorbidities, delayed admission (> 3 days), and Paxlovid (Pfizer, Freiburg, Germany) treatment significantly lengthened the NCDs.

Conclusions: Our results call for special concern for full and booster vaccination of the elderly, which will effectively protect from progression of COVID-19 to non-mild state. In the meantime, symptomatic COVID-19 patients should be treated as soon as possible.